HDDR各向同性NdFeB磁特性研究
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摘要
HDDR (Hydrogenation-Disproportionation-Desorption-Recombination)是继快淬法后制备各向同性粘结磁粉的又一有效方法。前人对HDDR的研究主要集中利用HDDR法制备各向异性粘结磁粉,且主要集中在新的工艺条件和方法,对HDDR制备各向同性粘结磁粉的反应条件的作用规律等因素考虑较少,对氢压的影响也研究较少。因此本实验采用热分析的方法对氢压的影响进行研究。
实验首先对HDDR制备NdFeB各向同性粘结磁粉部分进行了工艺优化,包括歧化阶段反应温度、时间对磁粉性能的影响；脱氢再化合阶段反应温度、时间对磁粉性能的影响。研究发现在歧化阶段剩磁、矫顽力、磁能积均在820℃歧化1.5h后获得最大值,在本实验条件下制备得到的磁体最佳性能为(BH)m=4.1MGOe, Hcj=12.2kOe,Br=4.5kGs。对脱氢再化合阶段的温度和时间条件进行研究发现,剩磁、矫顽力、磁能积均在820℃脱氢再化合1.0h后获得最大值,在本实验条件下制备得到的磁体最佳性能为(BH)m=3.398MGOe, Hcj=8.592kOe, Br=4.162kGs。
在研究氢压对反应条件、磁粉性能的影响中发现。氢与富Nd相、Nd2Fe14B在170℃开始发生吸氢放热反应,在发生吸氢反应前真空升温可提高NdFeB合金的表面活性,降低吸氢反应温度。在700℃出现歧化峰,歧化产物主要为NdH2+x、Fe2B及α-Fe相。随着歧化氢压升高,NdH2+x相越稳定性,越有利于歧化反应的进行,歧化峰左移,起始歧化温度降低,对样品进行XRD分析,利用谢乐公式计算晶粒大小发现,随着歧化氢压的升高,晶粒逐渐增大。随着脱氢氢压的升高,脱氢峰右移,脱氢反应起始温度升高,对样品进行XRD分析,利用谢乐公式计算晶粒大小发现,随着脱氢压力的增大晶粒减小
对脱氢再化合反应进行热力学计算发现,820℃氢压30kPa以及800℃氢压20kPa的脱氢条件下,脱氢再化合反应不能进行。通过对不同温度、不同脱氢氢压进行正交试验,实验发现脱氢再化合阶段剩磁、矫顽力、磁能积分别在10kPa、820℃获得最佳性能(BH)m=3.89MGOe, Hcj=10.07kOe, Br=4.69kGs;20kPa、840℃获得最佳性能(BH)m=4.47MGOe, Hcj=11.03kOe, Br=4.89kGs; 30kPa、860℃获得最佳性能(BH)m=3.49MGOe, Hcj=10.69kOe, Br=4.20kGs。随着脱氢氢压的升高,脱氢再化合反应速率下降,最佳性能获得的反应温度也升高。
HDDR (Hydrogenation-Disproportionation-Desorption-Recombination) is effective method for fabricating bonded magnetic powder of isotropic after rapid quenching method. Previous studies have focused on the HDDR prepared by anisotropic bonded magnetic powder, and focused on the new processing and preparing methods, while the rules about reaction condition of the HDDR prepared by isotropic bonded magnetic and influence of the hydrogen pressure was considered little, so the method of thermal analysis was introduced to study the effects of hydrogen pressure in thispaper.
Parts of the preparing process of HDDR isotropic NdFeB magnetic powder was optimized firstly, which include selection of temperature and time in disproportionation phase, temperature and time in recombination phase. The research shows that in the process of disproportionation, the best condition in our experiment was 820℃and t=1.5 hours, and highest value is that (BH)m=4.1MGOe, Hcj=12.2kOe, Br=4.5kGs. In the process of recombination, the best condition in our experiment was 820℃and t=1.0 hours, and highest value is that (BH)m=3.398MGOe, Hcj=8.592kOe, Br=4.162kGs.
Hydrogen pressure in the study on the reaction conditions by DTA were found that Nd-rich material and Nd2Fe14B matrix phase activates hydrogen absorption at 170℃with exothermic, heating under vacuum can increase the NdFeB alloy surface activity, reduces hydrogen absorption reaction temperature before reaction. Disproportionation peak appeared at 700℃, and products of disproportionation were NdH2+x, Fe2B and a-Fe phase. As the hydrogen pressure is increased, NdH2+x phase more stability, more conducive to disproportionation reaction, peak of disproportionation left, the temperature of reaction decreases, XRD showed that grain size calculated by Scherrer formula found that with the hydrogen pressure of disproportionation increased, the size becomes bigger. With the increase of hydrogen pressure in recombination, peak of recombination shifted to the right, the temperature of recombination increases, XRD showed that grain size calculated by Scherrer formula found that with the hydrogen pressure of recombination increased, the size becomes smaller.
Recombination reaction by thermodynamic calculations and found 30kPa,820℃, 20kPa,800℃under the recombination reaction can not occur. The orthogonal test method was adopted to explore the influences of temperature and hydrogen pressure on the magnetic properties, the best condition in our experiment was 10kPa,820℃, and highest value is that (BH)m=3.89MGOe, Hcj=10.07kOe, Br=4.69kGs, best condition 20kPa,840 ℃best value (BH)m=4.47MGOe, Hcj=11.03kOe, Br=4.89kGs, best condition 30kPa,860℃best value (BH)m=3.49MGOe, Hcj=10.69kOe, Br=4.20kGs. With the increase of hydrogen pressure of recombination, the rate of recombination reaction decreased, the temperature of the best performance also increased.
实验首先对HDDR制备NdFeB各向同性粘结磁粉部分进行了工艺优化,包括歧化阶段反应温度、时间对磁粉性能的影响；脱氢再化合阶段反应温度、时间对磁粉性能的影响。研究发现在歧化阶段剩磁、矫顽力、磁能积均在820℃歧化1.5h后获得最大值,在本实验条件下制备得到的磁体最佳性能为(BH)m=4.1MGOe, Hcj=12.2kOe,Br=4.5kGs。对脱氢再化合阶段的温度和时间条件进行研究发现,剩磁、矫顽力、磁能积均在820℃脱氢再化合1.0h后获得最大值,在本实验条件下制备得到的磁体最佳性能为(BH)m=3.398MGOe, Hcj=8.592kOe, Br=4.162kGs。
在研究氢压对反应条件、磁粉性能的影响中发现。氢与富Nd相、Nd2Fe14B在170℃开始发生吸氢放热反应,在发生吸氢反应前真空升温可提高NdFeB合金的表面活性,降低吸氢反应温度。在700℃出现歧化峰,歧化产物主要为NdH2+x、Fe2B及α-Fe相。随着歧化氢压升高,NdH2+x相越稳定性,越有利于歧化反应的进行,歧化峰左移,起始歧化温度降低,对样品进行XRD分析,利用谢乐公式计算晶粒大小发现,随着歧化氢压的升高,晶粒逐渐增大。随着脱氢氢压的升高,脱氢峰右移,脱氢反应起始温度升高,对样品进行XRD分析,利用谢乐公式计算晶粒大小发现,随着脱氢压力的增大晶粒减小
对脱氢再化合反应进行热力学计算发现,820℃氢压30kPa以及800℃氢压20kPa的脱氢条件下,脱氢再化合反应不能进行。通过对不同温度、不同脱氢氢压进行正交试验,实验发现脱氢再化合阶段剩磁、矫顽力、磁能积分别在10kPa、820℃获得最佳性能(BH)m=3.89MGOe, Hcj=10.07kOe, Br=4.69kGs;20kPa、840℃获得最佳性能(BH)m=4.47MGOe, Hcj=11.03kOe, Br=4.89kGs; 30kPa、860℃获得最佳性能(BH)m=3.49MGOe, Hcj=10.69kOe, Br=4.20kGs。随着脱氢氢压的升高,脱氢再化合反应速率下降,最佳性能获得的反应温度也升高。
HDDR (Hydrogenation-Disproportionation-Desorption-Recombination) is effective method for fabricating bonded magnetic powder of isotropic after rapid quenching method. Previous studies have focused on the HDDR prepared by anisotropic bonded magnetic powder, and focused on the new processing and preparing methods, while the rules about reaction condition of the HDDR prepared by isotropic bonded magnetic and influence of the hydrogen pressure was considered little, so the method of thermal analysis was introduced to study the effects of hydrogen pressure in thispaper.
Parts of the preparing process of HDDR isotropic NdFeB magnetic powder was optimized firstly, which include selection of temperature and time in disproportionation phase, temperature and time in recombination phase. The research shows that in the process of disproportionation, the best condition in our experiment was 820℃and t=1.5 hours, and highest value is that (BH)m=4.1MGOe, Hcj=12.2kOe, Br=4.5kGs. In the process of recombination, the best condition in our experiment was 820℃and t=1.0 hours, and highest value is that (BH)m=3.398MGOe, Hcj=8.592kOe, Br=4.162kGs.
Hydrogen pressure in the study on the reaction conditions by DTA were found that Nd-rich material and Nd2Fe14B matrix phase activates hydrogen absorption at 170℃with exothermic, heating under vacuum can increase the NdFeB alloy surface activity, reduces hydrogen absorption reaction temperature before reaction. Disproportionation peak appeared at 700℃, and products of disproportionation were NdH2+x, Fe2B and a-Fe phase. As the hydrogen pressure is increased, NdH2+x phase more stability, more conducive to disproportionation reaction, peak of disproportionation left, the temperature of reaction decreases, XRD showed that grain size calculated by Scherrer formula found that with the hydrogen pressure of disproportionation increased, the size becomes bigger. With the increase of hydrogen pressure in recombination, peak of recombination shifted to the right, the temperature of recombination increases, XRD showed that grain size calculated by Scherrer formula found that with the hydrogen pressure of recombination increased, the size becomes smaller.
Recombination reaction by thermodynamic calculations and found 30kPa,820℃, 20kPa,800℃under the recombination reaction can not occur. The orthogonal test method was adopted to explore the influences of temperature and hydrogen pressure on the magnetic properties, the best condition in our experiment was 10kPa,820℃, and highest value is that (BH)m=3.89MGOe, Hcj=10.07kOe, Br=4.69kGs, best condition 20kPa,840 ℃best value (BH)m=4.47MGOe, Hcj=11.03kOe, Br=4.89kGs, best condition 30kPa,860℃best value (BH)m=3.49MGOe, Hcj=10.69kOe, Br=4.20kGs. With the increase of hydrogen pressure of recombination, the rate of recombination reaction decreased, the temperature of the best performance also increased.
引文
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[3]Strnat K, Hoffer G, Olson J. A family of new Cobalt-Base permanent magnet materials. J Appl Phys,1967,38(3):1001-1002
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